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UNIVERSITY OF CALIFORNIA Agricultural Experiment Station 

College of agriculture e. j. wickson, acting director 



(September, 1906.) 




The frequency with which this Station is called upon to give advice 
in regard to soils, whether in respect to the quality and best adaptations 
of new lands, or the correction of faults observed in those already under 
cultivation, renders it desirable to formulate some general explanations 
on the subject, which may in many cases enable the farmer to come to a 
definite forecast or conclusion, without individual consultation and ad- 
vice; or, when this is not attainable, may so instruct him that he can 
forward to the Station such definite statements of facts, and samples 
properly taken, as will convey the data needful for a full understanding 
of the situation. 

Very many conditions contribute toward the agricultural character- 
istics of a soil, and any one or more of these may, under certain circum- 
stances, be the controlling one. It is therefore essential that the infor- 
mation given by the farmer should be as complete as possible, since with- 
out it the trouble involved in the examination of samples will as a rule 
not be justified, as lacking the proper basis for an intelligent opinion or 
fruitful advice. 

Not many years ago it was the custom to ascribe the languishing or 
death of trees and crops to some "poison" contained or generated in the 
soil. In California, the poison theory still maintains itself to some extent, 
in ascribing the trouble observed to "alkali," even though no manifes- 
tations of that substance may ever appear on the surface. But unless a 
soil at the end of the dry season shows a white crust or dust of alkali 
salts on the surface, there is no reason whatever to suppose that alkali has 
anything to do, directly, with injury to the crop or trees; for such injury is 
rarely done to the roots in the soil, but usually by the accumulation of 
alkali salts near the surface. 

Leaving aside the case of special diseases, such as are due to the 
action of fungi, insects, or other organisms, it has now become usual, in 
this State at least, to attribute any faulty or defective growth of culture 
plants to some chemical defect in the soil, and to address to the Station 
the question what fertilizer should be used to make up the deficiency. 

Extended investigation of our soils has shown that in California, far 
more than in the Eastern States, very few soil-materials exist that would 
not naturally produce good crops for some 18 or 20 years without 
fertilization, provided they are of sufficient depth and are adequately 
supplied with moisture. In many cases, forty or fifty years is a low esti- 
mate for the duration of profitable production. When, therefore, in orch- 
ard or vineyard, it is noticed that after growing well from three to five 
years, or even longer, the trees or vines begin to languish, and sometimes 
even to die, it is not as a rule reasonable to conclude that it is for want 
of any needful ingredient in the soil. This is especially true of the "die- 
back" in orchards — the dying of the tips of branches in the tree-tops, 
which, when not clearly due to scale insects or fungous attack, is nearly 
always caused by some defect in the subsoil, at or near the ends of the 
roots; such as hardpan, dry gravel layers, bottom water, or the like. Such 
defects cannot, of course, be cured by fertilization; and the farmer him- 
self can, by the exercise of common sense and digging to the ends of the 
roots, satisfy himself very quickly of the existence or absence of such 
defects, which can often not be recognized when samples are sent to the 
Station, but must be observed on the spot. 

Importance of the Subsoil. — In our dry climate, depth of the soil is of 
the first importance, since the roots of culture plants must go deep in 
order to be secure against the summer's drought. As the latter renders 
the surface soil, which in the humid region is the main source of supply 
to plants, practically unavailable during a large part of the season of 
growth, it is clear that here, more than anywhere, the depth and qaulity 
of the subsoil is of the greatest importance, and should be investigated in 
all cases by the intending purchaser of land before investing. The omis- 
sion of this simple precaution has led to untold losses and disappoint- 
ments, which have been the more frequent as the formation of a "hard- 
pan" at a depth corresponding more or less to the penetration of the 
annual rainfall, is of unusually frequent occurrence in this State. The 
richest surface soil may be utterly useless for general farming purposes 
if underlaid, at a depth varying, according to the nature of the soil, from 
one to four feet, by a hardpan or clay impervious to the roots of plants. 
As a rule it is not practically feasible to maintain, even by irrigation, a 
proper supply of moisture in a light soil limited in depth by impervious 
hardpan at two or three feet, even in cases where the roots of the crop 
do not habitually penetrate beyond that depth; in the case of fruit trees 
and vines (the roots of which in certain lands are limited only by a depth 
beyond fifteen or twenty feet) the objection to such lands in their nat- 
ural condition is insuperable, unless the difficulty can be overcome by 
dynamiting the tree-holes. 

An equally fatal objection, so far as tree culture is concerned, lies 
against too close proximity of bottom water to the surface. The roots 
of culture plants will bear submergence only for a very limited time with- 
out injury (forty days is considered the extreme limit in the case of vines 
and orchard trees) ; hence lands periodically overflowed and not very 
perfectly drained are unsafe for the planting of trees, as the roots will 
decay where the air is excluded; and such injured roots will inevitably 

render the tree unproductive, if they do not kill it in the course of time. 
The same effects are of course produced wherever leaky irrigation ditches 
cause the rise of water to within a few feet of the surface. Drainage, 
not fertilization, is the effective remedy in such cases. Yet such lands 
may be well adapted to the growth of certain shallow-rooted crops, par- 
ticularly of those having a short period of growth. 

On the other hand, in some kinds of sandy lands, the breaking up of 
what might be considered a hardpan, as compared with the surface soil, 
may almost wholly destroy its cultural value by rendering it "leachy, ' ' 
so that neither irrigation water nor fertilizers will be sufficiently retained 
for the profitable growth of crops. It is therefore clearly necessary that 
not only the existence of such underground layers be definitely ascer- 
tained, but also that their particular nature be considered with respect 
to the kind of surface soil, and to the practically feasible or profitable 
uses to which the land is intended to be put. 

Examination of the Subsoil. — Outside of adobe tracts, an exceedingly 
simple and effective device for subsoil examination is a square steel rod 
not less than a quarter of an inch in diameter, well pointed at one end, 
and provided at the other with a stout iron ring for the reception of a 
cross-handle, such as is used for post-hole augers. With such a prod or 
sounding-rod, not less than five feet in length, and made to penetrate the 
soil by means of a slight reciprocating motion aided by the weight of 
the operator, the exploration of the subsoil for hardpan, dense clay layers 
or bottom water becomes a matter of a few minutes; and a few hours' 
time suffices to thus explore extended tracts, and perhaps save bad in- 
vestments of thousands of dollars; or, at the very least, to convey very 
valuable information as to the probable defects or virtues of the land, 
not only with respect to root penetration, but also with regard to irriga- 
tion, drainage, etc. It is easy also to detect thus, with a little practice, 
the presence of underlying layers of quicksand, gravel, or other loose 
materials through which irrigation water would waste, or which would 
present the capillary rise of bottom moisture within the reach of plant 
roots, by the large iterspaces between their grains. Any remaining 
doubts as to the nature of such underlying materials at particular points 
can then quickly be settled by the use of a post-hole auger. The latter 
serves also most conveniently for the taking of samples to be submitted 
for examination by the Station; but it should be remembered that in no 
case should any one sample represent the average of more than one foot 
in depth; and that whenever a material change of resistance to the 
auger's penetration is observed, the depth at which such change occurs 
should be noted, and a sample taken of the material causing such change, 
again not to exceed in any case the additional depth of one foot. 

The extreme depth to which the boring and taking of samples should 
reach depends not only upon the nature of the soil, but also upon that of 
the crop expected to be planted. The tap-root of a pear tree will in 
almost any soil require, for normal development, a depth of six feet at 
least; hence pear trees should never be planted in shallow soil. Almonds 
and peaches, on the other hand, will be content with half that depth, if 
necessary, provided the soil be rich enough and the supply of moisture 
adequate, but not excessive. 

In coarse, gravelly soils, as well as in hard adobe, it may become 
necessary to use the pick and spade (not shovel) to dig a vertical hole 
of sufficient width and depth for observation, and for the taking of 
samples to be examined. In digging such holes the same rule as above 
given for the post-hole borings should be observed. 

When, after careful examination of the soil and subsoil as described 
above, doubt remains as to the cause of any difficulty observed, or when 
for special reasons a more thorough examination of the case is desirable 
or necessary, samples representing the average of not more than one foot 
each may be taken, from the surface down to such depth as may be 
thought needful in each case, in accordance with the directions given be- 
low, for transmission to the Experiment Station at Berkeley. 

Value of Soil Examinations and Analyses. — It is necessary to refer 
here to some erroneous ideas and prejudices regarding the practical ap- 
plication of the results obtained from soil examination, and from chem- 
ical soil analysis especially. While some imagine that such an analysis 
can, like the assay of a mineral, tell them just what the soil is worth, or 
what it needs to make it productive, others have, on the contrary, been 
taught to believe that chemical soil analysis is utterly useless, and can 
convey no information useful to the farmer. As usual, the truth lies be- 
tween the two extremes. 

The physical (mechanical) and chemical conditions existing in a soil 
are of equal importance for plant growth; if either be seriously defective 
the farmer will labor under a great disadvantage. But usually the chem- 
ical deficiencies are more readily remedied by fertilization than physical 
defects, which should, therefore, receive the first investigation and con- 

But when the physical conditions are found satisfactory, chemical 
analysis will, in virgin soils, or in such as have been under cultivation 
only a short time, give most definite and practically useful information 
as to the means of improvement, if such be necessary. The habit of 
many Eastern immigrants, of asking how to fertilize, right at first, the 
exuberantly fertile natural soils of California and of the arid region gen- 
erally, is a solicitude wholly uncalled for. The farmer cannot, however, 
make chemical analyses himself; and even if made by a chemist, they 
may be of little use unless the method employed be known and consid- 
ered, and the results intelligently interpreted by an expert. This in the 
case of soils long cultivated and fertilized is often a very difficult prob- 
lem, to be successfully handled only when the cultural history of the soil 
area in question is known. Hence the disappointments so commonly com- 
mented on in the Eastern States and in Europe, where nearly all soils have 
been artificially changed. 

With a knowledge of the composition of a virgin soil and of the crops 
that have been or are intended to be grown upon it, we are in a position 
to give to the farmer forecasts of what is most likely to benefit his soil 
most, with the least expense, and with at least equal probability of correct 
judgment as in the case of a physician prescribing for a patient. In both 
cases the practical test is the final one; in both, random experimenting or 
quacks may hit or miss the mark. 


In taking soil specimens for examination by the Agricultural Experi- 
ment Station of the University, the following directions should be care- 
fully observed— always bearing in mind that the examination, and espe- 
cially the analysis, of a soil is a long and tedious operation, which can- 
not be indefinitely repeated. 

First.— When ascertaining the respective merits of new lands, do not 
take samples at random from any points on the land, but consider what 
are the two or three chief varieties of soil which, with their intermixtures, 
make up the cultivable or cultivated area, and if necessary, sample these, 
each separately; then sample the particular soil on which you desire in- 
formation, noting its relation to these typical ones. 

Second.— As a rule take specimens from spots that have not been 
changed from their original condition of ' ' virgin soils, ' ' e.g., not from 
ground frequently trodden over, such as roadsides, cattle-paths, or small 
pastures, squirrel holes, stumps, or even the foot of trees, or spots that 
have been washed by rains or streams, so as to have experienced a not- 
able change, and not be a fair representative of their kind. 

Thir cL — Observe and record carefully the normal vegetation, trees, 
herbs, grass, etc., of the average virgin land; avoid spots showing un- 
usual growth, whether in kind or in quality, as such are likely to have 
received some animal manure, or other outside addition. 

Fourth.— Always take specimens from more than one spot judged to 
be a fair representative of the soil intended to be examined, as an addi- 
tional guarantee of a fair average, and mix thoroughly the earth taken 
from the same depths. 

Fifth. — After selecting a proper spot, pull up the plants growing on 
it, and sweep off the surface with a broom or brush to remove half- 
decayed vegetable matter not forming part of the soil as yet. Dig or 
bore a vertical hole, like a post-hole, removing a foot in depth, and note 
at what depth a change of tint occurs. In the humid region, or in humid 
lowlands of the arid, this will usually happen at from six to nine inches 
from the surface, and a sample taken to that depth will constitute the 

In California and the arid region generally very commonly no change 
of tint occurs within the first foot, sometimes not for several feet; hence, 
especially in sandy lands, the "soil" sample will usually be taken to 
that depth, so as to represent the average of the first foot from the sur- 
face down. 

Samples taken merely from the surface, or from the bottom of a hole, 
have no definite meaning, and will not be examined or reported upon. 

Place the soil sample upon a cloth (jute bagging should not be used 
for the purpose, as its fibers, dust, etc., become intermixed with the soil) 
or paper, break it up, mix thoroughly, and put at least a quart of it in a 
sack or package properly labeled for examination. 

This specimen will, ordinarily, constitute the "soil. " Should the 
change of color occur at a less depth than six inches, the fact should be 
noted, but the specimen taken to that depth nevertheless, since it is the 
least to which rational culture can be supposed to reach. 


In this way take a sample of each foot separately to a depth of at 
least three feet; preferably four or five; especially in the case of alkali 
soils, or suspected hardpan. 

Sixth.— Whatever lies beneath the line of change, or below the mini- 
mum depth of six inches, will constitute the "subsoil." But should the 
change of color occur at a greater depth than twelve inches, the "soil" 
specimen should nevertheless be taken to the depth of twelve inches only, 
which is the limit of ordinary tillage; then another specimen from that 
depth down to the line of change, and then the subsoil specimens beneath 
that line. 

The depth down to which the last should be taken -will depend on 
circumstances. It is always necessary to know what constitutes the 
foundation of a soil, dowu to the depth of three feet at least, since the 
question of drainage, resistance to drought, root-penetration, etc., will 
depend essentially upon the nature of the substratum. In the arid re- 
gion, where roots frequently penetrate to depths of ten or twelve feet or 
even more, it is frequently necessary to at least probe the land to that 
depth, or deeper. 

The specimens should be taken in other respects precisely like that 
of the surface soil, each to represent the average of not more than twelve 
inches. Those of the materials lying below the third foot from the sur- 
face may sometimes be taken at some ditch or other' easily accessible 
point, and if possible should not be broken up like the other specimens. 

If there is hardpan or heavy clay present, an unbroken lump of it should 
be sent, for much depends on its character. 

Seventh.— When in the case of cultivated lands it is desired to ascer- 
tain the cause of differences in the behavior or success of a crop on 
different portions of the same field or soil area, do not send only the soil 
which bears unsatisfactory growth, but also the one bearing normal, good 
growth, for comparison. In all such cases try to ascertain by your own 
observations whether or not the fault is simply in the subsoil or sub- 
strata; in which case a sample of surface soil sent for examination would 
be of little use. In such examinations the soil probe will be of great 
service, and save much digging or boring. 

Eighth. — Specimens of alkali or salty soils should preferably be 
taken toward the end of the dry season, when the surface layers will 
contain the largest amount of salts. A special sample of the first six 
inches should in that case be taken separately by means of a post-hole 
auger, and then, in a different spot close by, a hole four feet deep should 
be bored, and the earth from the entire four-foot column intimately mixed 
before the usual quart sample is taken. Samples of the plants growing 
on the land should in all cases be included in the package, as they indi- 
cate very closely the agricultural character of the land. 

All samples taken while the land is wet should be air-dried before send- 
ing; in the case of alkali soils this is absolutely essential. 

Ninth. — All peculiarities of the soil and subsoil, their behavior under 
tillage and cultivation in various crops, in wet and dry seasons, their 
location, position, "lay," every circumstance, in fact, that can throw 
any light on their agricultural qualities or peculiarities, should be care- 


fully noted, and the notes sent by mail. Without such notes, specimens can- 
not ordinarily be considered as justifying the amount of labor involved in 
their examination. Any fault found with the behavior of the land in 
cultivation or crop-bearing should be especially mentioned and described. 

The conditions governing crop-production are so complex that even 
with the fullest information and the most careful work, cases are found 
in which as yet the best experts will be»at fault. 

Send by express, prepaid, to ' ' Agricultural Exj)eriment Station, Berkeley, 
California. ' ' 

Always mark the name and postoffice address of the sender on the box or 
package, and on each package contained therein; also on a pencil-written 
label inside of each package. The Station staff cannot undertake to re- 
label such packages, and thus avoid the mistakes and losses liable to happen 
as the result of this omission. 

It should be distinctly understood that samples sent for examination 
must take their place and turn on our docket, and can only in excep- 
tional cases be advanced for immediate report. Usually such requests 
come in by scores in the autumn and winter, just prior to planting time, 
with the request for immediate report. This cannot, as a rule, be given; 
work already in hand must have precedence. Persons desiring such ex- 
amination should not wait until so late in the season, if they wish to 
make use of the results for tlit, coming, planting season.